Testing apparatus



F. H. BEST.

TESTING APPARATUS. APPLICATION man MAY14.1920.

1,414,397,- Patented. May 2,1922.

UNITED sr *I ma nani) H. BEST, or wnsrFiELD, Niiw Jiiitsnr,"AsslIGNoi-t` trofAMERICANwTELEPHON AND TnLnenArn: COMPANY, CORPORATION or NEWORKJ j TESTING APPARATUS.

Application filed May ifi, i920. serial Na.3e1,462. 7

To all whom tmag/ concern Be it known that I, FRED' l/Bnsi','resid-v tus, and -is concerned particularly with, methods of and means for determining the combined transmission eliciency of a telephone instrument and the line circuit thereof.- It is particularly applicable to Vsubscribers circuits in service, and is described herein with special reference thereto, but itk is to be understood that the invention isnot limited thereof. y

, VIn its preferred form of embodiment, the invention proposes to employ thefwires of the subscribers circuit in av so-called simplex circuit, consisting of the wires of the subscribers circuit in parallel with each other and to this particular application ,connected at both ends to ground, for sendingtesting energy from the central office to the subscribers station; converting this energy into sound energy by means of a re-` ceiver or other telephonic translating device of known characteristics; reconverting the sound energy into electrical energy in the Vsubscribers circuit by placing` `the aforementioned receiver against a transmitter or ref ceiver of the subscribers set and determining the amount of electrical energy which reaches the central otlice.

Y In a modification of the invention, the

c testing current may be sent to the subscribers station over the metallic circuit and returned to the central oilice over the simplex circuit, but the former lmethod is preferable to the latter for the reason that the comparatively weak current which flows baclrto the central office is not subject to suchdisturbances-as ground potentials or other noises .caused by the ground connections of the simplex circuit. v

A good understanding of theinvention may now behad from the following descrip-vk tion thereof, havingreference to the accom'- panying drawing, in which VFigure 1 is a diagrammatic view showing the preferred form` land. arrangement of apparatus embodying; .the invention,and F ig. 2 4a similar View showing the modification thereof. c c

. Similar characters of reference designate similar'parts in each ofthe views.- y

In Fig; 1, reference numerals 1 and 2 desigksubscribers station the by a telephone instrument, comprising ithe y ployed. l

nate the lin@J conductors of `a subscriberscir cuit extending between v`a 'central oiiiceA,

and a subscriberis station B. At the central oiiice the Vcircuit terminates in the usualjacls which,"however, havebeen omitted 'in the drawing for tliesake of simplicity-and at the circuit is completed usual transmitter T,- and receiver R.- The particular type of circuit arrangement-by 1 means of which'thetransmitter and receiver are vassociated with eacliiotherand withthe line circuit, is immaterialto the present i-nvention, it being understood that any of the usual circuit `arrangements may be em-1 To make 1a' test of `the transmission et' ciency of the subscribers circuit andinstru- Vmentl combined, the testmanat the central voffice bridges'a retardation coil `3 across 'thev line wires and connects `a source of testing f currentl 4l;l between the midpoint of. this coil and ground. Y' The testinan at the substation B bridges a coil "5 across the line wires and connects a receiver Rfpbetwe'en the midpoint ofV this coil Vand ground. 4These connections 1 complete a simplex circuit between the central olice and the substation, which circuit comprises the testing'source for the coil,

the wires 1 andv 2in parallel with each other,

thecoil 5 and receiver R to; ground return.

The currentfrom thetesting soiirce'.,causes response of the receiverlRf, andthe sound energy thus generated is-impressed onfthe distance from the transmitter, as, for eX- vtransmitter T of the subscriber?s instrument .by placing the receiverR" at a predetermined ample,'again'st'the mouthpiece. f The "sound y energy causes transmitter. Tftogenerate .elec- .trical energy inproportion to lits-efficiency, which energy iiows. overthemetallicfcircuit, VJformed by conductors 1 and 2in series, tothe c. central oilice Awherevit 'enters a .measuring apparatus in icated at M. This apparatusiis l preferably a transmission measuringset of anyV suitable.; type, such, for example, as is i described` inthe patent to 0. B. Blackwell, No. 1,261,096, 'dated April2, 1918. amount of current which" returns to the central Oliice` is ank indication ofthe combined The eiiiciency oftransmission of the subscribersj instrument. c

To 4determine circuit andthe transmitter of his telephone etciency. of the sub-V scribers receiver .in combination with the linecircuigthe .test man' atthe substation places the receiver R against the receiver B, thus causing the same to generate a cur-V rent which is transmitted bythe subscribers circuit to the central oiiicc, where 4may be measured by the measuring set M.

lnorder to approach as nearly aspos-` y sible tothe conditions Which obtainV during of the subscribers insti u ment. Y Yis placed against the testing receiver R',

the actual use ot the subscribers circuit and instrument, it is desirable that the itrequencies of current for which the above tests are made 'should be oit aboutV the same range vas that ot the natural voice. vThe lsource i isithereflfore lpreferably a frequency band generator, the 'frequency ot which varies rapidlyover'the voice range, or part thereof, and ivhicl'i'gives results which closely for R" should, moreover, be one of knovvn characapproximate theiconditions obtaining actual Vvoice currents. The receiver teri'stics so that allowances maybe made for the etliciency ot conversion thereof; This is particularly necessary Where it is desiied to 'compare tests made by means ot different testing receivers.

In the modification.illustrated in Fig, 2,

the-testing currentsource is connected in series With 'Wires l and .2 so that this current flows over the subscribers vmetallic circuit andjcauses response otrthe receiver R This receiver andcau'ses the same to send current over the simplex circuit back to the central otifice, Where it is measured by means of the device M, connected between the midpoint orthe coil 3 vand ground. rThis methodV is applicable to the transmitter only if the same is of the electromagnetic type, the ordinary carbon button transmittel1 being nonreversible in its operation. rlhis method is not as reliable as the lirst, for the reason thatV the comparatively iveal; currents rc- `and receiverl by the testfiiian'at tliesubf station.

Instead'ot theretardation coils S and 5- aiiy other impedances, such aslresistances,

may "be used to setr up the simpler; circuit as will be readily understood. Many other changes and modi'cations maybe made in [the A'apparatus'embodying the invention, and the method for practising the same, .the scope oit the invention being limited only as'defined bytheappeiided claims; f' i V/Vhat I'claim is:

5 1., The method 'of determining eiiif `ciencylof transmission of a'subscribers telephone instrument and circuit thereof, which consists in sending testing current trom'the' central ofhce to thesubstation over the sub-l r scribers line lvvires in parallel With each other, converting this energy at the substatioiiinto sound energy, reconverting the sound energy into electrical energy bymeans A ot av translatinggdevice or the subscribers instrument, causing this energy to iioW back tothe central office through the line Wires in series with each other, and ascertaining the amount of energy Whichis thustranse mitted to the central office. Y

2. The method of determining the ymission cilicieiicy of a telephone instrument and the line circuit associating the said iny trans- Ystrument With a central office, Which'consists o in causing a ioiv of testing current overA said line Wires from the said central o'liice'to i said substation,-converting said energy into sound enrgj at the substation, reconverting the same 'into electrical energy bymeans ofV a translating device oit the subscribers instrument, causing g said electrical A energy to flow `over said line ivi-res to Vthe central oftice, and determining theamount-of saidY energy reaching the office.r

The method oit determining vtheV etticiency of a telephone instrument and its line circuit, which consists in causing theV HOWl ot testing current from one end ot thefcircuit to the other through the line Wires in series `Withcach other, converting the elec'- trical energy reaching said other end Ainto sound energyV by means or a'translatingde-l vice ot the subscribers instrument, reconvei'ting thesound energy thus'created into electrical energy by means orr an auxiliary telephonie translating device, transmitting the reconverted' energy oversaid line Wires iii parallel tothe lirst end of the circuit,-L

aiid determining the amount of energy received at the said firstveiid.

il. The method ot determining the transmissionv etticiencyV of a' Vsubscribers circuit and telephone instrument,'\vhich consistsin causing the'tlow of current approximating in frequency characteristic that of theyiiat-` uial voice from the central office to the subv station over the lineV ivireswin 'parallelfvvith each other, causing the Vs'aid'current t0 actuate a translating device forconverting electrical energy into sound, operativelyassociating l said 'Y translating deviceY `With the transmitter and receiver of the subscribers instrument one afterthe other, and measur# ing the electrical: energy which iscaused to enter the' central oflice by the saidtransmitter and receiver' respectively.

5. Inan apparatus ordeterininingthe vtransmission efficiency of a telephone instrument and the line circuit thereof, meansl 'for associating the Wires of saidline circuitciii simplex circuit, asource of Atestingcurreiit i associated With 7'one end 'of vsaid liner," means ries with each other, and' ascertaining the for connecting said source in one of said circuits for transmitting testing energyto the subscribersstation7 means thereat for converting the testing energy into sound energy, and reconverting the same into electrical energy, said means comprising a vtranslating device oi' the subscribers instrument, means for causing return flow ot said vreconvertedv electrical energy over the other circuit to said iirst end of the line, and means for determining the amount of energy reaching the said end. Y

6. The apparatus of claim 5 in which the circuit Jor transmitting the testing energy to the subscribers Astation is the simplex circuit and the circuit 'for'the return flow` is the line circuit. n Y y L '7. The combination with a telephone instrument and circuit thereforfextending be` tween a central office and the' said instrurnent, of conducting elements bridged `on said Vcircuit adjacent its ends, a' source of current lating device of the said instrument, andl means at the central office for ascertaining the current, entering said oiiice due to the.

response of the last mentioned translating device. Y Y Y i 8. The method of determining the etliciency off transmission of a subscribers cir-V cuit, which consists in sending 'testing current from the central oii'ice to the substation over ,the subscribers linelWires in parallel with each other, translating the energy thereof at the substation and applying it to the circuit consisting of said line Wires in Se-v amount ot energyv which is thus to the central ofice.

9.The method of determini-ng they ei ciencyv of transmission cfa line, 'which contransmitted -sists in sending testing current from oneend of the line Vto the lother over itstivo Wires in 'parallel7 translating' this energy and apr plyingl it to send current over the 'circuit comprising the said two Wires in series,and' kascertaining the ramount of energy Which'v is thus transmitted tov the initial sending end ofthe line. l0. The method of determining'the eiii.-y

ciency of transmission ct a line consisting.

of tWoparallel conductors, which consists in sending energy one Way over the line, translating this: energy atl the receiving end of the line and sending it baclrthe opposite .Way over the line,` and determining the amount of energy received at thevinitial sending end of the line, the transmission in one of the tivo Ways being over the twoV conductors of the line in parallel and the other of the two waysbeing oyer'the saineftwo conductors in series, f

ll. The method of determining the etliciency oftransmission of a subscribers telephonecircuit, whichconsists in sending test-"` Y i ing current fromV the central office to the sub# station over the subscribers line Wires, trans'- lating this energy at the substation and-applying it to generatev current in the circuit comprising said line Wires, and ascertaining the amount of energy which is thustrans-v mitted tothe central office, the transmission one Way, as aforesaid, being over the sub- `missionthe other Y* Way, asv aforesaid being overthe said linervvires in series.

In testimony whereof, I -have signed myV name yto this specification this 13th of' -May, 1920.

so scribers line Wires in parallel, and the trans- FRED n. BEST. 

